Amoxcillin + Clavunic acid

The entire evidence base for this question is a single 2020 Russian study, and it is not a clean test of the drug you asked about.

The study enrolled 100 patients with moderate acute bacterial rhinosinusitis and compared two groups: one got amoxicillin/clavulanate plus Polydexa with phenylephrine spray, the other got the same antibiotic plus oxymetazoline spray [1]. That is the key problem. The control arm is not a placebo or no-spray group. It is another active decongestant. So the trial can only show whether one nasal spray beats another nasal spray when both patients take the same antibiotic. It cannot tell you whether adding Polydexa to amoxicillin/clavulanate helps at all, because every patient got a spray.

The reported result is that the Polydexa group had faster improvement in subjective symptoms, nasal swelling, discharge, and X-ray findings by day 3 [1]. But the allocation method is not described, so you cannot rule out that sicker patients were put in one arm [1]. Worse, any patient whose treatment was changed on day 3 was dropped from the analysis entirely [1]. That is a per-protocol analysis, not intention-to-treat. It biases toward the treatment that looks better because the failures vanish.

On safety, the study says nothing useful. No serious adverse events are reported, but the follow-up is days, not weeks, and the sample is 100 people [1]. That is far too small to catch rare harms like allergic reactions, Clostridioides difficile colitis, or the known risk of antibiotic-associated diarrhea. There is no long-term safety data because none was collected.

The honest verdict: this single, small, conflicted study shows one decongestant spray may beat another on top of the same antibiotic. It does not prove Polydexa adds benefit, and it provides essentially no safety evidence. If you are weighing this drug, the burden is on the prescriber to show why the antibiotic alone is insufficient, because the retrieved record cannot. Confidence: low that the spray adds real benefit; no evidence at all on long-term safety.